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MP573 Microphone preamplifier / Re: MP573 LED not behaving correctly

« Last post by JPK on August 30, 2025, 09:04:49 AM »

It does make sense!
What we do is remove the cover of the XLR plug to access the pins and connect the meter to them.

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MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« Last post by musicarr on August 28, 2025, 06:47:45 PM »

Another question: what tolerance is recommended for the capacitors? 1%, 5%, 10%, or is 20% fine, too? Do tolerances differ for different kinds of capacitors used in these audio units, or is it the same pretty much across the board? Thanks.

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MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« Last post by musicarr on August 28, 2025, 02:42:27 PM »

Great! Thanks for the info. I know what to look for now.

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MP573 Microphone preamplifier / Re: MP573 LED not behaving correctly

« Last post by davidfloegel on August 28, 2025, 09:46:02 AM »

Ah I see, that makes more sense. 

I’m sorry if this is a dumb question but at which points do I measure the voltage? If the XLR is plugged in to the preamp while sending a signal, I’m not sure where to measure. 

I hope that makes sense!

Thanks for your patience!

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MP573 Microphone preamplifier / Re: MP573 weird behavior (no volume after 20)

« Last post by JPK on August 28, 2025, 08:38:56 AM »

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MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« Last post by JPK on August 28, 2025, 08:37:17 AM »

KEMET, KYOCERA, Vishay.

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MP573 Microphone preamplifier / Re: MP573 LED not behaving correctly

« Last post by JPK on August 28, 2025, 08:35:12 AM »

You must not go through a mic but instead connect a balanced cable between an output of your converter and the preamp mic input.
Then send a sine signal to this output and measure the amplitude with the DMM on AC Volts connected between pins 2&3 of the XLR. The measurement must be done while the output is connected to the pre input.

38

MP573 Microphone preamplifier / Re: MP573 weird behavior (no volume after 20)

« Last post by camarada78 on August 27, 2025, 06:05:20 PM »

FIXED - it was a bridge solder from a previous fix i've made. 

Thanks a lot for the help. 

have a good day.

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MP573 Microphone preamplifier / Re: MP573 weird behavior (no volume after 20)

« Last post by camarada78 on August 27, 2025, 02:47:45 PM »

My voltages, in reference to TP3, are as follows:

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MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« Last post by musicarr on August 27, 2025, 02:29:21 PM »

Thanks for the confirmation. Are there brands that you are familiar with that you recommend?